Section (8) blockdev
blockdev — call block device ioctls from the command line
−v] command [ command... ] device [
−−report [ device... ]
Print a report for the specified device. It is possible to give multiple devices. If none is given, all devices which appear in /proc/partitions are shown. Note that the partition StartSec is in 512-byte sectors.
Display help text and exit.
Print version and exit.
It is possible to give multiple devices and multiple commands.
Get alignment offset.
Print blocksize in bytes.
Get discard zeroes support status.
Get filesystem readahead in 512-byte sectors.
Get minimum I/O size.
Get optimal I/O size.
Get max sectors per request
Get physical block (sector) size.
Print readahead (in 512-byte sectors).
Get read-only. Print 1 if the device is read-only, 0 otherwise.
Print device size in bytes.
Print device size (32-bit!) in sectors. Deprecated in favor of the −−getsz option.
Print logical sector size in bytes – usually 512.
Get size in 512-byte sectors.
Reread partition table
Set blocksize. Note that the block size is specific to the current file descriptor opening the block device, so the change of block size only persists for as long as blockdev has the device open, and is lost once blockdev exits.
Set filesystem readahead (same like −−setra on 2.6 kernels).
Set readahead (in 512-byte sectors).
Set read-only. The currently active access to the device may not be affected by the change. For example filesystem already mounted in read-write mode will not be affected. The change applies after remount.